I have a Michael Phelps Swim Spa Signature Model that is 2,325 gallons. Just drained and refilled with untreated well water and filtered out the precipitated iron with a couple of changes of filters. My problem is getting the Ph in the range that is optimum for the Chlorine. I test the PH (after aeration and liberation of CO2 ) at least at 8.0 (test kit only goes up to 8.0 so it may be about 8.4 or 8.5, which is common in my fish rearing aquaculture systems.
Anyway, an acid demand test doesn't even come close to the amount of Muriatic Acid to add to bring the Ph down to 7.4 to 7.6, I'm assuming because my Ph is above the maximum Ph of the test kit? As due to the logrithmic Ph scale 8.4 or 8.5 is 4 to 5 times the base of 8.0. Additionally the total alkalinity is about 350 mg/l which as we know acts as a buffer fighting Ph change. Total hardness is quite hard in the 500 plus range.
When I do get the Ph down where it should be it bounces right back again by the next day no doubt due to the high alkalinity and aeration.But once I do get enough Muriatic Acid in the water to bring the Ph to the right level to stay there the Total Alkalinity is dangerously low. So the remedy for bringing the Ph back up is to add Sodium Bicarbonate (Backing Soda). You'll never guess what that does to the Ph.
Thoughts?